1. Field of Invention
The invention relates to an ink ribbon cartridge for use in a recording device, and more specifically to an ink ribbon cartridge including an exchangeable ink ribbon having a broad width.
2. Description of Related Art
When printing is performed for forming an image on a plain paper using a thermal printer, normally an ink ribbon cartridge is used because it is easy to exchange and simple to handle. Usually, an ink ribbon cartridge includes a broad-width ink ribbon when the thermal printer is a thermal line printer.
In such an ink ribbon cartridge, the ink ribbon is wound around a supply tube and extends to a takeup tube. An ink layer is formed on one surface of the ink ribbon. A spool without a gear is provided at one end of each of the supply tube and the takeup tube, and a spool with a gear is provided at other end of each of the supply tube and the takeup tube. All the spools are provided with a flange. The supply tube and the takeup tube are rotated in their circumferential direction by driving force transmitted via the gears.
When an ink ribbon cartridge is removed from the printer or placed by itself on a table top, for example, or when an operator picks up the ink ribbon cartridge and moves it around, the ink ribbon can undesirably loosen because the spools become freely rotatable with respect to the cartridge case.
Japanese Patent-Application Publication (Kokai) No. HEI-8-276630 discloses a configuration for overcoming this problem. Specifically, a pair of tubular spools on which an ink ribbon is wound are rotatably supported in a cartridge case. A compression coil spring is interposed between one end of each spool and first side wall of the cartridge case. The other end of each spool is formed with a groove engageable with an protrusion formed in an opposite second side wall of the cartridge case. The configuration is provided for moving the spools toward the first side wall so the protrusions and grooves fall out of engagement when the ink ribbon cartridge is mounting in a printer.
On the other hand, when the ink ribbon cartridge is removed from the printer, force of the compression coil spring moves the spools in their axial directions, and the protrusions engage with the grooves, thereby preventing the spools from rotating. In this way, the ink ribbon is prevented from loosening.
Also, Japanese Utility-Model-application Publication (Kokai) No. HEI-6-81749 discloses another type of ink ribbon cartridge. A pair of spools on which an ink ribbon is wound are freely rotatably supported in internal of a cartridge case. A compression coil spring is interposed between one end of each spool and a first side wall of the cartridge case. A flange with a large diameter is provided to the other end of the each spool. A friction plate is adhered either an outer surface of each of the flanges an opposite second side wall of the cartridge case confronting the outer surface of each flange.
With this configuration also, when the ink ribbon cartridge is removed from a printer, force of the compression coil springs move the spools in their axial directions, so that the outer surface of each flange is brought into pressing contact with the second side wall of the cartridge case, thereby preventing the spools from undesirably rotating. Therefore, the ink ribbon will not loosen.
However, with this configuration, operations for exchanging the ink ribbon are troublesome. That is to say, when the spools with a spent ink ribbon are removed from the cartridge case, there is a danger that the compression coil springs will fall off the cartridge case. Even if the compression coil springs do not separate from the cartridge case, in order to remove the spools from the cartridge, the compression coil springs need to be once greatly compressed.
Further, when mounting the spools with an unused ink ribbon into the cartridge case, the spools cannot be mounted in the compression coil springs unless the compression coil springs are once greatly compressed. For these and other reasons, the existence of the compression coil springs makes operations for exchanging the ink ribbon troublesome.
When the spools are replaced each time a spent ink ribbon is replaced, this wastes resources and increases the costs. Therefore, the spools are removed from the supply tube and the takeup tube with the spent ink ribbon, and mounted onto new supply tube and takeup tube with a fresh ink ribbon, and then mounted back into the cartridge case. At this time, the geared spools must be set at correct ends of the supply tube and the takeup tube and at correct locations in the cartridge case, otherwise the ink ribbon will not be arranged in a correct orientation in the cartridge case.